Light-emitting diodes (LEDs) have been used to provide illumination in industrial and commercial environments. LEDs are also used in TVs, computers, smart phones, and tablets. Although the light emitted by most LEDs appears white, LEDs have peak emission in the blue light range (400–490 nm). The accumulating experimental evidence has indicated that exposure to blue light can affect many physiologic functions, and it can be used to treat circadian and sleep dysfunctions. However, blue light can also induce photoreceptor damage. Thus, it is important to consider the spectral output of LED-based light sources to minimize the danger that may be associated with blue light exposure. In this review, we summarize the current knowledge of the effects of blue light on the regulation of physiologic functions and the possible effects of blue light exposure on ocular health.

This paper investigates the illuminance needed to detect trip hazards for pedestrians walking after dark. In previous work, it was assumed that the critical obstacle height is 25&#8201;mm: further review of accident data and foot clearance data suggests instead that 10&#8201;mm is the critical height. Eye tracking records suggest a tendency for obstacles to be detected approximately 3.4&#8201;m ahead. Interpretation of obstacle detection data suggests horizontal photopic illuminances of up to 0.9&#8201;lux are required for peripheral detection of a 10&#8201;mm obstacle 3.4&#8201;m ahead, according to the scotopic/photopic ratio of the lighting and the age of the observer.

Tony Price and Steve Fotios point out that while road lighting can be a significant counter measure to accidents, and that higher levels might help, the presence of road lighting does not guarantee all accidents will be avoided.

An experiment to investigate peripheral detection performance during a driverâ€™s transition between lit and unlit sections of road was undertaken. The results suggest that when a driver moves from a lit to an unlit section of road their detection performance decreases almost immediately to that expected for the conditions of the unlit section and that there is no significant change in the subsequent 20-minute period. Tests were conducted at three luminances (0.1, 1.0 and 2.0&#8201;cd/m2): while an increase from 0.1 to 1.0&#8201;cd/m2 improved detection, a further increase to 2.0&#8201;cd/m2 did not. Lighting of two S/P ratios (0.65, 1.40) was examined at 1.0&#8201;cd/m2: this did not suggest an effect on detection performance. Taken together, these results suggest that, in the current context, visual performance reached a plateau at 1.0&#8201;cd/m2.

Outdoor light at night (LAN) is an increasingly prevalent type of environmental pollution. Studies have demonstrated that outdoor LAN can disrupt circadian rhythms, potentially contributing to insomnia, cancer, cardiovascular disease, and metabolic changes in humans. We investigated the association of outdoor LAN with depressive symptoms and suicidal behaviors in South Korean adults.

Methods

This study used data from the 2009 Korean Community Health Survey, a representative sample dataset. Study population consisted of 113,119 participants for the assessment of depressive symptoms and 152,159 participants for the assessment of suicidal behavior. Depressive symptoms were measured using the Korean version of the Center for Epidemiologic Studies Depression Scale (depressive symptoms, score of > 16). Suicidal behaviors were defined as the experience of suicidal ideation or attempt. Outdoor LAN was estimated by satellite data from the National Centers for Environmental Information.

Results

Participants with depressive symptoms or history of suicidal behaviors were more likely to have exposure to outdoor LAN than those without depressive symptoms or suicidal behaviors. Compared with adults living in areas exposed to the lowest outdoor LAN, those living in areas exposed to the highest levels had higher likelihood depressive symptoms (OR = 1.29; 95% CI: 1.15â€“1.46) or suicidal behaviors (OR = 1.27; 95% CI: 1.16â€“1.39). Significant dose-response relationships were observed between outdoor LAN and the odds of depressive symptoms and suicidal behaviors.

Conclusion

Outdoor LAN was found to be significantly associated with depressive symptoms and suicidal behaviors, suggesting that it may be an environmental contributor to mental health problems.